Show your slant 6 a body!
I bought mine from a Dodge Dealer in FL about 1990 or so. They had a stack of about 20 of them on the table at the show! Asking price was $10.00 each. In my infinate wisdom I only bought 1 for myself....UGH! I then bought the Accessory Set (Includes - 12 chrome plated Screw Washer sets, Chrome Oil Filler Cap, & both Valve Cover Grommets... $5.00!) I figured they would always be available - my bad.
Now, IF you are interested here is the info on them from my 1994 Mopar Performance Catalog:
Chrome Valve Cover - 1960 to 1980 engines P3690742,
1981 to 1987 engines - P4529063,
Valve Cover Accessory Set - P4120272.
As for the 1960's ribbed Valve Covers - I have seen them but they are not listed in the 1994 Catalog - Sorry!
HAPPY HUNTING!
Here is mine on my 1970 Dart GT when I installed it in 1996:
Hope this helps!
Later,
Bruce B.